Senvion has identified heating issues in the rotor bearings of some its offshore wind turbines, and the German manufacturer says it has tapped external specialists to validate what it believes is the root cause and verify the solution.

"Anomalies have been registered in the rotor bearings of offshore turbines in our 5M and 6XM series. All of the anomalies share the characteristic of a rise in temperature in the bearings,” explains Verena Puth, a Senvion spokesperson. "An endoscopic examination of the bearings identified wear. We then conducted an analysis that established inadequate lubrication of the bearings as the root cause."

Puth says the company first noticed the issue last summer, and according to Senvion’s investigation, “Remedial action can be taken by directly injecting additional lubricant.” The company is now working with third-party examiners to further ensure the problem and its solution have been correctly identified.

Although Senvion did not specify how many installed turbines might have been affected, Puth says the issue poses no danger.

“The anomaly manifests itself at an early stage through a rise in temperature,” she says. “All Senvion systems are continuously checked by our monitoring system, thereby ensuring that rises in temperature are identified immediately. This means that nobody is at risk at any time.”

“We have a state-of-the-art product in a technological area that is still young,” she adds. “It is entirely normal for this technology to be subject to adjustment.”

Nonetheless, the issue appears to have placed at least one of Senvion’s turbine orders in jeopardy. The company currently has a contract with RWE Innogy for the delivery, installation and service for 54 of its turbines at the Nordsee 1 offshore wind farm in the German North Sea. The developer is reportedly seeking a backup turbine supplier to ensure the project will remain on schedule if Senvion does not fix the issue and fails to deliver the machines before the permitted construction timeline.